Just make sure you use "buddyforms" as post type to make sure the meta box is only loaded in the BuddyForms edit screen.

In the above example we add a checkbox to the meta box.

You can use any kind of form element. As long as you make sure you add it to the "buddyforms_options" array all the rest like saving and validating will be done automatically. Just make suer you use the structure "buddyforms_options[YOUR OPTION]" in your form element name.